The invention relates to a spiral link belt comprising a multiplicity of synthetic resin helices in which the windings of one helix mesh in zipper fashion with the windings of the adjacent helices without any tensile or compressive spring-like stess, and pintle wires inserted into th channels formed by the meshing windings of each two helices with the windings of the helices penetrating into the material of the pintle wires. The helices are of oval shape with heads at the winding arcs that are widened in the longitudinal direction of the helices and the interiors of the helices are stuffed with filler material.
In the spiral link belt disclosed in German published Application No. 31 35 140 a widening of the windings heads is discernible from FIG. 2. Such widening seems to be a result of thermosetting the spiral link belt.
U.S. Pat. No. 4,346,138 discloses that, in the course of making the helices, a minor widening of the winding heads is effected in order to ensure engagement of the helices before the pintle wires are inserted.
German published Application No. 24 19 751 discloses a spiral link belt in which the individual helices in the spiral link belt are under spring-like tensile stress. In combination with substantial widening of the winding heads, this can impart to the helices a strong coherence such that the winding heads act as coupling heads or coupling flats which lock the helices together without pintle wires as set forth in the last paragraph of the description and claim 3 of this application.
Applicants' co-pending U.S. application based on German published application No. 35 04 373 discloses the reduction of air permeability by causing the windings of the helices to cut especially deeply into the material of the pintle wires so that the penetration depth is equal to or greater than the wire thickness of the helices. To this end especially profiled pintle wires, or pintle wires sheathed with softer material, are employed. However, such pintle wires require additional production steps and thereby increase the production costs.